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Michel Euler, Associated Press
Israel's Defense Minister Ehud Barak gestures as he speaks during a session at the World Economic Forum in Davos, Switzerland, Friday, Jan. 27, 2012. The meeting lasts until Jan. 29.

DAVOS, Switzerland — Israeli Defense Minister Ehud Barak said Friday the world must quickly stop Iran from reaching the point where even a "surgical" military strike could not block it from obtaining nuclear weapons.

Amid fears that Israel is nearing a decision to attack Iran's nuclear program, Barak said tougher international sanctions are needed against Tehran's oil and banks so that "we all will know early enough whether the Iranians are ready to give up their nuclear weapons program."

Iran insists its atomic program is only aimed at producing energy and research, but has repeatedly refused to consider giving up its ability to enrich uranium.

"We are determined to prevent Iran from turning nuclear. And even the American president and opinion leaders have said that no option should be removed from the table and Iran should be blocked from turning nuclear," Barak told reporters during the annual meeting of the World Economic Forum.

"It seems to us to be urgent, because the Iranians are deliberately drifting into what we call an immunity zone where practically no surgical operation could block them," he said.

Barak called it "a challenge for the whole world" to prevent a nuclear-armed Iran but stopped short of confirming any action that could further stoke Washington's concern about a possible Israeli military strike.

Separately, U.N. Secretary General Ban Ki-Moon urged a resumption of dialogue between Western powers and Iran on their nuclear dispute.

He said Friday that Tehran must comply with Security Council resolutions and prove conclusively that its nuclear development program is not directed to making arms.

"The onus is on Iran," said Ban, speaking at a press conference. "They have to prove themselves that their nuclear development program is genuinely for peaceful purposes, which they have not done yet."

Ban expressed concern at the most recent report of the International Atomic Energy Agency that strongly suggested that Iran's nuclear program, which it long has claimed is for development of power generation, has a military intent.

IAEA chief Yukiya Amano said at a Davos session that "we do not have that much confidence if Iran has declared everything" and its best information "indicates that Iran has engaged in activities relevant to nuclear explosive devices."

"For now they do not have the capacity to manufacture the fuel," he said. "But in the future, we don't know."

In spite of his tough words to Iran, Ban said that dialogue among the "three-plus-three" — Germany, France and Britain plus Russia, China and the United States — is the path forward.

"There is no other alternative for addressing this crisis than peaceful ... resolution through dialogue," said Ban.

Ban noted that there have been a total of five Security Council resolutions so far on the Iranian nuclear program, four calling for sanctions.

As tensions have been on the rise recently, some political leaders in Israel and the United States have been speaking increasingly of the possibility of a military strike to eliminate, or at least slow down, what they allege is a determined effort by Iran to obtain nuclear weapons.

John Daniszewski contributed to this report.